1. Field of the Invention
The present invention relates to a shift control device in a hydrostatic transmission in which a hydraulic closed circuit is formed between a swash plate type hydraulic pump and a swash plate type hydraulic motor and a swash plate holder for supporting a motor swash plate of the hydraulic motor is tiltably supported on a stationary structure through a trunnion shaft fixedly mounted on the swash plate holder, the shift control device being constructed so that the angle of the motor swash plate is adjustable to control the volume of the hydraulic motor in order to control a shift ratio.
2. Description of the Prior Art
It is known to connect a hydraulic servo motor to a motor swash plate so as to enable the angle of the motor swash plate to be lightly adjusted (see Japanese Patent Publication No. 38467/84).
In the above prior art, the hydraulic servo motor is complicated in structure and expensive and for this reason, an increase in cost of a shift control device can not be avoided.